This invention relates to the self-propelled cranes and more particularly to self-propelled cranes with non-telescopic boom.
The various types of cranes are well known. In order to lift the heavy and most important large-size load are used the cranes and derricks with luffing jib and/or cranes with a telescopic main boom. Some cranes for increasing of the boom luffing characteristics use a luffing jib section in addition to the telescopic boom, as it is mentioned, for example, in the U.S. Pat. No. 4,063,649. Accordingly to this patent the mobile crane has a telescopic boom comprising a lower section, an intermediate section slidable telescopically within the upper end of the lower section and an upper section slidable telescopically within the upper end of the intermediate section. Extension means such as hydraulic rams are provided to position the intermediate section with respect to the lower section and the upper section with respect to the intermediate section so that the overall length of the telescopic boom may be adjusted to any desired value between a maximum and a minimum limit.
The lower end of the boom intermediate section is pivoted to a horizontal base unit so as to permit luffing movement of the boom.
The base unit is mounted upon a road vehicle chassis and is arranged for rotation with respect to the chassis about a vertical axis on a slewing center.
For basic duties of the crane, a load is suspended by a hoist rope which passes over a sheave at the outer end of the boom upper section to a winding drum. By varying the extension of the boom and/or the luff angle, the horizontal distance between the slewing center and the hoist rope can be varied so as to permit the lifting of loads located within a range of radius of action from the slewing center.
For fly duties of the crane in order to increase a range of radius of action from the stewing center for lager size load lifting, is used an additional luffing jib (fly jib), which is secured to the outer end of the boom intermediate section and the hoist rope (cable) passes over a sheave at the fly jib outer end. For any combination of telescopic boom extension and fly jib the distance between the slewing center and the hoist rope new position at the end of the fly jib is greater than the corresponding value of the distance between the slewing center and the hoist rope position at the end of boom upper section.
Such modification (supplementary equipment) provides increasing of boom-out, but leads to decreasing of the lifting load weight considering weak and non-moored construction of the fly jib, and also requires the reinstallation operations for crane basic duties and for crane fly duties. The crane supplementary equipment presented in the U.S. Pat. No. 4,673,093 is for mooring a crane and is intended to provide a heavy load lifting by the assembly of interconnected guy wires (cable) between a gay mast, which is not connected to a luffing jib and not directly connected to a main boom, and long, massive stationary crane foundation (e.g. pontoon). The possibility to lift large-size load in such crane is provided by the standard luffing jib.
These types of cranes have complex mooring system comprising the separate gay cable and luffing cable, requiring additional hoist blocks and frames and the described improvements by the mentioned U.S. Pat. No. 4,673,093 is not applicable for the mobile cranes, which has mostly a boom and not provided by the expensive luffing jib system.
As has been mentioned above, the most of the small and medium self-propelled cranes (mobile cranes) have a boom and do not include a luffing jib, being unable to lift a large-size load, as shown, for example, on FIG. 1 (on the drawing is presented a hypothetical/conventional lifting of the load).
Some cranes have a need to arrange the large-size load for lifting. The hoisting arranging equipment for large-size load is described in the U.S. Pat. No. 5,314,262. According to the invention, a supplemental equipment for load arrangement includes two motor driven cable drums, fixed cable points associated with the load arranged on the frame of the load, cable rollers arranged on a roller support, as well as hoisting cables guided between the cable fixed points and the cable drums. The cable drums are of a double-thread design wherein each of the cable drums feeds of two cables. The cable drums, together with their drives, are supported on the load in parallel and offset by a drum diameter. The distance between the cable supported by a first drum and cable supported by a second drum approximately corresponds to a spacing distance between a first set of rollers and second set of rollers on the roller support when the cable drum is fully wound with cable (the roller support and spreader are in an upper most position). The distance between the cable fixed points of cables from the first drum and the fixed points of cables from the second drum likewise corresponds approximately to the distance between the first set of cable rollers and the second set of cable rollers. The first set of cables on the first drum and the second set of cables on the second drum run off the drum in an inward direction (the first set of cables move inwardly, towards the second set of cables and the second set of cables move inwardly towards the first set of cables as they run off during lowering).
Such load arranging supplementary equipment is complex and expensive.
Thus, the known small and medium self-propelled cranes can not provide the lifting of heavy and large-size loads.
Accordingly, several objects and advantages of the present invention are to provide an improved self-propelled crane to lift the heavy and large-size loads.
It is another object of the invention to increase the self-propelled crane possibility to lift the loads with the higher weights.
It is still another object of the invention to provide the increased the luffing of the small and medium self-propelled cranes.
It is further object of the invention to increase the self-propelled crane possibility to lift the loads with the larger sizes.
It is still further object of the invention to provide the horizontal level of the lifting loads.